جستجوی مقالات مرتبط با کلیدواژه « weir » در نشریات گروه « آب و خاک »

In this study, a special type of sharp-crested weir is called sharp- crested morning glory weir (SCMGW) is introduced. Due to the special shape of this weir, high measurement accuracy in low discharge, and in flood and sudden discharges, less back water profile is expected upstream. On the other hand, there is no discontinuity in their stage-discharge relationship. Assuming the occurrence of a critical flow in the weir crest, the general stage-discharge relationship was extracted for this type of weir. The next step was to correct this assumption, considering that the assumption of the occurrence of a critical flow in the weir crest is accompanied by an error, and consequently the stage-discharge relationship obtained based on this assumption is not accurate. For this purpose, by measuring 57 experiments on 5 types of this weir, the stage-discharge relationship was extracted and it was shown that for a specific stage, the measured flow is greater than the calculated analytical flow. A correction coefficient was applied to the analytical relation with the aim of matching the stage-discharge analytic relationship with the measurement. This correction factor was optimized and extracted using the gene expression programming method as a function of the weir height-to-head ratio (p / H) and the a / n ratio (a and n parameters of the weir geometric shape). The results showed that the modified discharge-stage relationship estimated the measured discharge values as R2 = 0.98, mean absolute error MAE = 0.442 liters and root mean square error of RMSE = 0.08 liters.

Side weirs are important structures in irrigation and drainage networks that are used as a protective structure upstream of reverse siphons and road underpasses. In this research, using laboratory data, for two positions of lateral overflow placement diagonally in the width change wall and directly and in the wall without change width, a new relationship based on the critical depth of flow on the weir to determine the discharge discharge weir (QW) are provided in rectangular channels with narrowing downstream of the weir. The results showed that the discharge capacity of oblique weir decreasing width downstream is more than normal overflows and also diagonal weirs located in the width reduction wall are more than the case where the weir is in the direct wall without width reduction. Finally, by comparing the relationships obtained from dimensional analysis in two types of overflows, it can be concluded that the flow rate of side weirs located in the diagonal wall of the transition section is about 7.50 percent higher than the case where the side is located in the direct wall of the weir. The reason is less interference of flow lines. Also, the narrowed part of the downstream acts as a barrier, increasing the depth of flow and less curvature of the flow lines, and the flow passes through this weir with less drop.

After Hamidieh Diversion Dam near the city of Hamidieh, Karkheh River is divided into two streams known as Hufel and Nissan. At the lower flow rates, Nissan makes up a greater share than Hufel due to the steeper slope of the former. This study attempted to construct a hydraulic structure to appropriately divide water flow in Hufel. In a laboratory experiment, a flume with a 90-degree bend was used at Islamic Azad University of Ahvaz. Various experiments were conducted at different widths and heights. Furthermore, this model was simulated through CCHE2D, the results of which were compared against those of physical and mathematical models. The results indicated that the weir height increased the deviation flow percentage to the Hufel stream due to rising water level. Moreover, the deviation flow percentage to Hufel was declined as the weir width was increased due to falling water level. At Hufel, the installation of rectangular weir in different dimensions yielded the minimum of 34.3% and the maximum of 61.5% increase in the flow rate. In the normal mode without any weirs installed, however, there would be an increase in the flow rate, as compared to the mode where a weir has been installed. This can be associated with the flow controlled by the weir. On average, the deviation flow rate was increased by 2.8% in the weir mode and 7.7% in the weir-less one. An increase in the Froude number from 0.21 to 0.38 led to a lower average deviation flow rate by 19.3%. Moreover, the results of the simulation through CCHE2D were demonstrated to be largely similar to those of physical model experiments. However, an increase in the Froude number did not lead to a decline in the deviation flow rate (i.e. it remained constant). This trend was inconsistent with the results of the physical model.

In this research, by using FLOW3D, the performance of non-linear (arced) piano key (PKW-NL) in plan and linear piano key weir (PKW-L), with equal length of weir, was compared. Results showed that nonlinearity of the weir caused 20% increase in the discharge coefficient. Investigating the velocity contours for these two weir models also showed that maximum velocity within the PKW-NL weir structure is about 30% lower than the PKW-L weir. Also, the performance of non-linear piano key weir was evaluated under inward (PKW-IC) and outward (PKW-OC) curvatures to the channel. Results showed that in the case of PKW-IC weir, the discharge coefficient was increased by 8% as compared to the PKW-OC weir. Investigating the pressure contours for these two weir models also shows that the average pressure within the PKW-IC weir structure is about 5% higher than the PKW-OC weir. This increase in pressure leads to a decrease in the speed and better distribution of flow over the weir keys.

weirs are widely used to measure flow, water deviation and flow control in open channels. So far, most of the weirs used in the diversion dams were linear. In this study, the effect of sediment properties transmitted in the main channel and intake channel has been studied by changing the magnification of the weir.

The research was carried out at the Hydraulic Laboratory of the Water Engineering Department of Bu-Ali Sina University. The experiments were carried out in flume lengths of 10 meters, width of 83 cm and height of 50 cm. weirs, gate and intake channels with accessories and reservoir of sediment collection were also designed and added to the collection. For testing, non-adherent sediment particles with a grain size of approximately the same size and with a diameter of 0.35 mm were used. Experiments were carried out with a layer of sediments of thickness of 4 cm and slope of 0.002 and in two discharges of 40 and 60 liters per second. At first, intake gate and sluice way was closed and a flow with a small discharge entranced until the flow passed on the weir. Then the discharge increased to 60 or 40 liters per second. Then the intake gate was opened to a certain amount and the experiments were carried out for a certain period of time. Then, the entered sediments into the intake channel and also the accumulated sediment in the mesh of the end of main channel were collected, dried and weighted, and the concentration of sediments entering the intake channel and also downstream of sluice way were calculated.

The results showed that, in equivalent intake discharge ratio, with increasing discharge from 40 liters to 60 liters, the concentration of sediments in the intake channel increases. Also in equivalent intake discharge ratio, increasing the weir magnification increases the concentration in the intake channel. Also the increase in intake discharge ratio and the increase of the sluice gate discharge ratio, increase the concentration of sediments in the intake channel. The same applies to the sluice gate. This means that increasing the magnification, increasing discharge, intake discharge ratio and sluice gate discharge ratio will increase the concentration of sediment input to the intake channel.

Increasing the magnification reduces the flow head and also reduces the flow depth in the upstream, and as a result, the shear stress rate of the flow increases, which results in the transfer of more sediment to the downstream and, consequently, to the intake channel. Increasing the opening of the intake gate and, consequently, increasing the intake discharge rate, also increases the concentration of sediments deposited to the intake channel, However, increasing the weir magnitude and also increasing the sluice gate discharge ratio has no Significant influence on the sediment concentration ratio of the canal intake to the main channel.

More than 75% of the rice cultivated land is located in the northern provinces of Mazandaran, Gilan and Golestan. In recent years, the second cultivation of rice has been developed. This research was carried out in Mazandaran province, Khazarabad region of Sari, for the Premature varieties of local Tarom during two seasons for second cultivation in (2016 and 2017). In this study, triplicate overflow was used to measure inlet and outflow discharges. Three lysimeter were used to determine the water requirement of the fields. The water requirement was calculated from the input difference, which included the amount of water input that was calculated by overflow, as well as rainfall and output, including (evapotranspiration, permeability of the lateral submerged area and drainage water) Also, the irrigation of three stages of crop, reproductive and rearing for the first crop of (2015) was estimated to be 1.10, 1/5, 1/2 The coefficient for the second cultivation of (2016) was ./98, 1.4, 1.03, and the second planting factor of 2017 was ./95, 1.34, 1/01 respectively. The results show that the amount of water requirement in the second cultivation of 2016 and 2017 is 33%, 27% less than the first crop of 2015 respectively. Also, the average of crop factor in three stages of growth in the second cultivation of 2016 and 2017 was 10% and 12%, respectively, compared to the first one of 2015. Therefore, in regions where there is a good level of rainfall during the second crop, it is possible to recommend the second crop of rice.

Considering the drought crisis and high consumption of water in paddy fields, it is useful to present strategies in order to increase irrigation efficiencies. However, one of the methods to increase productivity in the agricultural development of cropping and ratoon culture that has an important role in the economy of rural households. Therefore, it is necessary to determine the amount of water needed for the second cultivation of rice and the cultivation of ratoon for water resources planning. This study was conducted in Mazandaran province, Sari. The local Tarom early varieties during two crop seasons in 1395 and 1396 years of regional ratoon also was conducted in 1396. To measure the input and output flows, triangular overflow was applied to the treatments and three lysimeters were used to determine the water requirement of the fields. Water use efficiency and water productivity were investigated in each treatment season. The results showed that the highest consumption efficiency was measured at 61% in ratoon cultivation. The water use efficiency in ratoon cultivation increased by 39% compared with the second cultivation of 1395 and 42% compared to the second cultivation of 1396. Water productivity in the second cultivation of 1395 and 1396 and ratoon cultivation in 1396 was 51%, 33% and 40%, respectively. Therefore, in areas with enough rainfall during the second cultivation and cultivation of ratoon, second cultivation of rice and rattan culture can be recommended.

Weir is one of the most applicable instruments for flow control and measurement in open channels. Accurate measurement of discharge in irrigation channels is vital for irrigation management. Weirs are designed as control sections for providing a unique relationship between the discharge and water head. In current study, theoretical and experimental characteristics of flow through a weir located in a horizontal circular channel were investigated. Choosing of this structure is due to lack of adequate studies on governing hydraulic equations of this kind of channels and its practical characteristics. In this research, discharge through the weir located at the end of a horizontal circular channel was developed from a theoretical viewpoint, and then calibration of this theoretical discharge equation was done via the discharge coefficient. The experimental data obtained in the study were also used to develop an empirical discharge coefficient relationship.
Theoretical discharge equation:The discharge equation of the circular weir ends up incomplete elliptic integrals of the first and second kinds, which are not very suitable for practical purposes due to their complexity. The theoretical discharge over the weir, Qt, can be expressed as:in which F(a,b) is approximated using the method of undetermined coefficients as:where g is the gravitational acceleration, h is the flow depth above the weir crest, D is the channel diameter, , , , and P is the weir height.
Introducing the discharge coefficient, Cd, yields the following equation for actual discharge, Q, of the weir.
Experimental setup and discharge coefficient equation: Determination of discharge coefficient, Cd, needs measuring the actual discharge (experimental or field data). The experiments were performed at the hydraulic laboratory of the Irrigation and Reclamation Engineering Department, University of Tehran. In order to collect experimental data, the weir was installed at the end of two horizontal circular channels with nominal diameters of 200 mm and 300 mm, and numerous measurements of different parameters that may have effect on discharge coefficient were carried out. An opening was provided on top of the pipes for flow head measurements by the point gauge. Water head over the weir crest was measured at a distance of 0.45 m upstream of the weir section. The weir plate was made of 10-mm-thick PVC sheet with a crest thickness of about 1 mm, and the downstream edge bevelled to a 45° angle (sharp-crested weir). For water heads over the weir crest smaller than 1.5 cm, in some cases clinging flow did occur and thus there was no atmospheric pressure under the lower nappe. Though, for heads greater than 1.5 cm a clear lower nappe profile with atmospheric pressure underneath was formed. Effects of surface tension and viscosity forces on the discharge coefficient, Cd, became pronounced at low water heads. Viscous and surface tension effects on discharge coefficient are neglected in this research. This is owing to operating range of the weir (minimum water head of 2 cm), which forbids surface tension effects and eliminates viscous effects. The experimental coefficient of discharge is computed for each data set collected in this study for known values of D, h, P and Q. A total of 350 tests were conducted to collect the data in the discharge ranges of 0.5 and 45 l/s. Suitable empirical equations for discharge coefficient were proposed using the 70% of the experimental data, and remaining data (30%) were used for validation procedure.
Proposed empirical equation for discharge coefficient: Using the curve-fitting technique, the following equation is obtained for CdThis empirical equation is valid for 0.095≤h/P≤1.8, 0.27≤P/D≤0.73 and 0.05≤h/D≤0.56. The assumptions made in deriving the above empirical equation of discharge coefficient are that the channel slope is horizontal, the flow is free and surface and viscous tension effects on Cd are negligible. A comparison of the experimental discharge coefficient with computed ones using the proposed empirical equation for all of the experimental data, the calibration data set and the validation data set showed that the computed discharge coefficient values are well within ±5% of the observed data for all three data sets. The average relative error of computed discharge coefficient using the proposed empirical equation for discharge coefficient Cd compared with the observed values is less than 5% for 95% of all experimental data. The results of this study reveals that a weir with low flow height is more sensitive to water flow depth, and weirs with more height are less sensitive to upstream flow head variation and thus are more reliable for flow measurement.

Weirs are hydraulic structures that are built for regulating, controlling and diverting water in the flow direction. Gabion structures are used extensively in water projects due to the ease of construction, permeability, accessibility and economic efficiency. Porous gabion structures are adaptable to the environment due to their material and performance and also are valuable from ecologic view point. In this study, 8 physical models of gabion weirs and 2 models of solid weirs were built for determining discharge coefficient in gabion rectangular broad crested weirs. Comparisons between gabion weirs with solid weirs were done and they showed that the discharge coefficient in gabion weirs was greater than that in solid weirs. In addition, the regression relations based on the dimensional analysis for the flow through gabion weirs were obtained for both the free and submerged conditions. Results showed that the discharge coefficient of gabion weirs in free condition was 16.7 % greater than that of the submerged condition.

Pivot weirs (sharp crested inclined weirs, Fig. 1-a) is frequently used for discharge measurement, controlling water surface and flow diversion. Some typical features of pivot weirs are: (a) overshot design for better water level control, (b) Their application as head gates, turnout or check structure which requiring low head loss and high accuracy, (c) ease of removing sediment deposit behind the weir, and (d) ability to manage and monitor on-site or operating remotely when connected to a supervisory control and data acquisition (SCADA) network. Kindsvater and Carter (8) derived a weir discharge equation based on energy and continuity equations. Hulsing (4) determined head-discharge relationship of inclined suppressed sharp crested weir with the slope of 3:3, 2:3 and 1:3 toward downstream and compared them with the equivalent normal sharp crested weir. In the USBR report on pivot weirs (regarding The Boulder Canyon Project,1948) the head discharge data of the suppressed pivot weir were presented in a channel with 5.5m length, 2.9m depth and 0.61m width. Some field experiments were also carried out in the IID (Imperial Irrigation District) on a trapezoidal cross-section (0.61 m bottom width) channel with pivot weir of 1.7m length, and two different widths of 1.63m. The flow rate (350-880 lit/s) was held constant and different angles (15-50°) calibrated instead of holding the angle constant and varying the flow rate. Some other laboratory tests were performed with Wahlin and Replogle (1994) on two pivot weirs with 1.2 m and 1.14 m width for the 0.61 m and 0.46 m length of blade and contraction factor of 0.925. RUBICON Company established an extensive operation on the application and automation of pivot weirs in irrigation channels in Australia (Www.rubicon.com). All previous studies concentrated on modifying the normal rectangular weir head-discharge equation so that it can be used for the pivot weirs. In this study, it is trying to derive a unique head-discharge equation for pivot weirs based on dimension analysis and critical discharge equation (implementing Ferro rule). This equation can be used for different inclined angles and side contractions. The obtained unique and simple discharge equation can be used in automation of this structure.
Material and In this research, experimental data consist of experiments carried out in hydraulic research institute of Tehran, Iran and experiments of USBR on Pivot weir with side contraction in 0.925 in the canal with 1.14 m width and 0.46 m blade length (Wahlin and Replogle, 1994). Experiments of the water institute of Tehran were carried out in the concrete rectangular weir with 10.30m long, 1m wide and 1m depth (Fig.2). Experimental model was consisted of canals, water supply system, dampers (avoided of turbulent flow upstream of pivot weir), pivot weirs, sluice gate at the end of the channel (make different tail waters). With respect to laboratory equipment’s, three pivot weirs with of 80×65, 60×55 and 40×40 (cm×cm) respectively length of the blade and the width was built and set 5.5 m far from the first of the canal. Discharge was determined from the calibrated weir located at the upstream of pivot weir. A manual point gauge with ±0.01 mm sensitivity was used to measure water surface levels.
Extraction of discharge equation: Dimensional Analysis based on Ferro rule (2000 and 2001) is used to determine the discharge formula of pivot weirs. Since the h-Q function is usually exponential, the relation between dimensionless parameters could be defined as Ferro rule.
The rating curve of the pivot weirs with different side contractions is compared with the normal suppressed rectangular weir (equal weir height) in Fig. 3. The discharge of normal suppressed rectangular weir was calculated from the discharge equation of Kindsvater-Carter and discharge coefficient of Rehbock (1) for the equal weir height and head of pivot weirs. For a constant water head, the discharge of pivot weir with a side contraction of 0.925 is more than the normal suppressed weir. When the weir plate is inclined to the bottom of the canal, because of the stagnation area behind the weir plate, the streamlines approach the weir blade smoothly and the energy dissipation is lower than for the normal weirs. The vortex behind the weir plate increases as the inclined angle increases and subsequently the discharge coefficient decreases. Reduction of discharge for a constant water head in contract weirs is simply justified by decreasing of the weir width. The α and β coefficients were obtained based on all experimental data. Discharge equation obtained based on critical depth-discharge equation.
In this study, based on dimension analysis a unique head-discharge relation was obtained which could be used for different inclined angels and side contractions. This equation is more appropriate than previous formulas which are modifications to the normal weir head-discharge equation. The accuracy of this equation was evaluated by different data sets including different inclined angle, side contractions, weir heights and also a wide discharge range. This equation could be used in the automated irrigation network easily.

Because of the fairly simple equations for accurate flow measurement and controlling the water level, weir and gate method is more useful than the separate weir, gate and partial flume methods. Since the flowing water in the channel always contains sediment particles and floating debris, they are deposited at the gate inlets and behind the weirs which reduces the size of the channel in the structure range and which reduces some problems such as neighboring land flooding due to overflow of water from the channel banks, threatening the structure stability and reducing the measurement accuracy. Using a combination of weir- gate model, in comparison with other conventional devices, will make it possible to get the actual conditions closer two main hypotheses derived from the relations and accurately measure the discharge coefficient. In this model, the deposited materials are easily passed through the gates and the suspended debris are easily passed over the weirs. One of the combined weir- gate structures is semi cylindrical weir- gate structure. Regarding about the form of the combined weir- gate structures, it has some advantages , including simple design, sediments and floating material flow, high flow discharge coefficient compared with other replaceable structures and its being economic. Semi Cylindrical gate turning around center Axis, for reason of rotation the center becomes Conversion to wire, wire gate with opening with different height.
The experiments were conducted in a rectangular flume with the length of 8 m, width of 0.282 m and height of 0.3 m in Soil Conservation and Watershed Management Research Institute. In this research, PVC pipes were used as semi cylindrical gate structures. The experiments were conducted for three diameters 70, 120 and 160 mm with height of the opening between zeros until radius, angles zero, 30, 45, 60 and 90 degree and differently discharging. Experiments were performed at a discharge limit of 2-27 l/s. In order to decrease turbulence of the flow, the gate was installed at the end 4 m of the flume. The ratio of cylindrical structure diameter to channel width (D/B) was in the range of 0.25 to 0.57 and the Froude number was in the range of 0.08 to 0.55.
Coefficient discharge of semi cylindrical structure and then dimensionless parameters of [H/P], [a/H], [ /H] and [Fr] against the discharge coefficient in the studied gate opening between zero until radius were investigated. According to result with decrease dimensionless parameter of a/H, discharge coefficient increased, So that the maximum Coefficient discharge rate of angle 90 degrees and minimum angle 0 degrees. Also in a constant of a/H for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains and has no change, shows that changes in diameter of semi cylinder have no significant impact on discharge coefficient. With increasing H/P for both curves upstream and the downstream, discharge coefficient increased. Also in a constant of H/P for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains. With constant of angles with increasing Freud for all angles, both the curvature of the downstream and upstream, /H decreased. Also in a constant of Freud and angles, with increasing the diameter of semi cylinder, /H remains. According to the result, discharge coefficient of semi cylindrical gates varies, in Experimental limit, from 0.45 to 1.45 which is more than that of sluice gates reported by the USBR. One of the reasons, this is ascribed to this is the difference between the amount of entrance, head loss in this structure, because when the flow approaches cylindrical gate, due to curvedness of the wall upstream, a gradual gathering of flow lines gives the aerodynamic method to entrance section, thus decreasing resistance against the flow and entrance head loss and increasing discharge coefficient. However, in sluice gates the vertical wall in entrance section is conducive to fast gathering of flow line, thereby increasing resistance against flow, increasing entrance head loss, and decreasing discharge coefficient relative to a semi cylindrical method.
The results showed that increasing Froude coefficient and decreasing the a/H (ratio of gate opening to upstream water depth) dimensionless parameter decrease, respectively increase the discharge coefficient and decrease head loss in all aspects of structural alignment. Within addition by increasing the H/P dimensionless parameter (ratio of upstream water depth to structure diameter) discharge coefficient increased. Results showed that the maximum and minimum values of discharge coefficient are related respectively to 90 degree and 0 degree angle.

Weir and Gate are widely used in control, diversion and measurement of flow in irrigation projects due to their simpler and relatively exact relationship. There are sediment and suspended materials in the direction of channels. The accumulation of sediments and suspended materials in the back side of weir and gate caused change of canal shape and reduction of water measurement accuracy. The combined model of weir- gate have the capability of passing settling down from under the gate and suspended materials over weir simultaneously and prevents from accumulation of sediment and suspended materials in the back side of the weir and helps to the accuracy of water measurement and passing flow. The present research investigated ten combined model of labyrinth weir- gate on the effects of plan shape change and gate height on discharge coefficient in the laboratory. The results showed that the existence of gate and increasing of opening height, increased discharge coefficient in combined model of labyrinth weir- gate. On the other hand, existence of gate in combined model of rectangular labyrinth weir- gate in low total upstream water height to weir height have higher effect on the increasing of discharge coefficient. Whereas in combined model of trapezoidal labyrinth weir- gate, with the same of total upstream water height to weir height, had uniform effect on the increasing of discharge coefficient. The results showed that increasing of upstream water height caused interference of water jets of cycles of labyrinth weir and also interference of water flow passing under the gate and flowing water over the weir. Therefore discharge coefficient was lower in deeper depths. On the other hand, in the same depth, the trapezoidal labyrinth weir had less flow interference with respect to rectangular labyrinth weir, which caused higher increase in discharge coefficient in combined model of trapezoidal labyrinth weir-gate with respect to combined model of rectangular labyrinth weir- gate.

Curved weirs in plan due to their special hydraulic conditions as well as long crest، have suitable capability in effective water surface regulation in irrigation canals and networks. Also، these weirs have high turbulence intensity in downstream and make better conditions for rivers، in environmental point of view. There are few studies regarding calculation of curved weirs’ discharge coefficient and their head discharge equation. In this study، using new optimization method of genetic programming، a dimensionless equation for discharge coefficient has been proposed based on two non-dimensional parameters of weir angel and ratio of water head to weir height. For training and testing of the proposed equation، experimental data of Kumar et al، have been used. Comparison of results obtained from this equation with the experimental data reveals high accuracy of the new equation of genetic programming. Mean absolute errors of the proposed equation for discharge coefficient have been calculated as 1. 36 and 1. 65 percent، for training and testing phases، respectively. This error for non-linear equation of Kumar et al، is nearly 9. 4 percent.

In Combined weir - gate structures، interaction of flow over weir and through gate brings up intense mixing and change bed shear stresses distribution. Hence، simulation of flow pattern in downstream of these structures is very complex. The object of this research is numerical modeling of combined flow over weirs and through gates by Flow3D software. Flow3D is a high accurate model in computational fluid dynamics for simulation of problem with complex geometry on wide limits of fluid flows in open channel hydraulic. By applying VOF method and RNG K-ε turbulent models، a series of simulation combined flow in weir - gate structure on rigid bed were performed and results were compared by some experimental data that carry out in this research. Results for the equation of Qup/Qin (equation 13) calculation error statistics software based on RMSE and R2 was evaluated and these values obtained 0. 0994 and 0. 992. Results of this research show that Flow3D with RNG K-ε turbulent model is appropriate to simulation of combined flow in weir - gate structure and estimation of free surface profile and discharge ratio passed over weir to under the gate.

The low efficiency and weak performance of Doroodzan irrigation and drainage network¡ and other irrigation and drainage networks in Iran¡ make researchers to evaluate and solve the problems. Water distribution and management of related structures are important research subjects. In Doroodzan irrigation network¡ radial gates and constant head orifices¡ control and deliver water to farms. Complexity of the radial gates hydraulic algorithms¡ and farmers interference in gates regulating¡ cause problems for water distribution. In the present study¡ the influence of weir elevation setting on offtaking discharge change was evaluated. The selected radial gate was closed about 20¡ 50¡ and 80% of the initial gate opening¡ and elevation of the external wasteway was raised about 7¡ 14¡ and 20 centimeter. Results showed that raising elevation of external wasteways to an elevation higher than internal wasteways¡ decreases the wastewater and the discharge changes in offtakes¡ and leads to easier management of the system.

In most cases flow control and measuring structures on open channels, are built in a length smaller than the channel width due to the high expenses or for corresponding to the channel cross section. Hydraulics of flow in such structures is different from full width structures. In the current experimental research the effect of contracting 2 sides of a cylindrical weir-gate on the combined discharge coefficient has been investigated. The experiments were done in a laboratory flume with 7.5 m length, 30 cm width and 46 cm height, using cylindrical weir-gate models with diameters of 75, 110, 125 and 160 mm, constant gate opening of 3 cm, similar contraction ratio for the gate and weir in the range of (0.2≤b/B≤1), and different discharges and flow depths for the free flow. The results showed that the combined discharge coefficient was directly related to the ratio of upstream water depth to the weir-gate height (H/P), the ratio of water head over the weir to upstream water depth (Hw/H), and the ratio of structure length to the channel width (b/B). On the other hand, when the ratio of (b/B) decreased, the rate of Cd changes vs. (H/P) decreased, too. At the end, the multiple nonlinear regression analysis was used to correlate the discharge coefficient of such structures to both hydraulic and geometrical effective parameters.

By combining weirs and gates the problems of sedimentation and floating materials upstream the weir and gate structure can be resolved. In combined structures a new hydraulic condition is created which is differing from hydraulic condition in weir and gate only structures. Due to jet flow passing through or under structure، the scour hole is formed downstream of structures that’s may endanger the stability of the structure. So determination of scour hole characteristics is attracted by researchers. The object of this study is numerical modeling of scour pattern downstream of combined flow over weir and under the gate by Flow3D software. For modeling the turbulence، RNG k-، k- and LES were used. Flow3D is a high accurate model in computational fluid dynamics for simulation of problem with complex geometry on wide limits of fluid flows in open channel hydraulic. By applying VOF method، a series of simulation scour pattern downstream of weir - gate structure were performed and results were compared by some experimental data. The results show that Flow3D with LES turbulent model can be used with high accuracy (with R2=0. 96، RMSE=0. 0117) to simulation of scour pattern and water surface profile in weir - gate structure.

Combination of weir and gate as a hydraulic measuring structure has advantages such as passing the float and settling materials (ice, wood, sediments, etc) simultaneously in compression using weir and gate separately. The flow through combined devices may be submerged when the downstream water level affect on discharge coefficient. In this study, the authors describe new experiments of both submerged cylindrical and sharp edge weir-gate to investigate the effects of geometric and hydraulic parameters on flow discharge. The experiments have been done on rectangular and horizontal small laboratory flume with fore cylinder sizes and also same sharp edge sheet for several flow rates and downstream water level. The results demonstrate that the discharge coefficient are affected by ratio of upstream depth to gate opening H/a, the ratio of upstream depth to height of structure H/P and the ratio of downstream water depth to upstream depth. Also, two submergence limits can be defined for combinational model. The first one depends on gate and it occurs when HTW/H=0.55-0.65 and the second one belongs to weir in HTW/H=0.8-0.85. Moreover, in the both sharp- edged and cylindrical combination models with increasing the submergence ratio, the trend of discharge coefficient decreases similarly and in a constant submergence ratio, the relative discharge coefficients of both models are similar.

The combined system of gate and weir is used for flow measurement in open channels. But in case the passing water has floating material and sediment it damages their performance and hence error of measurement will increase. In order to solve this problem، weir and gate can be combined and a concentrated hydraulic system known as weir-gate can be developed، thus allowing sediments transportation from under the gate and floating particles on weir. The principal goal of this study was to investigate the passing flow characteristics by trapezoidal weir and sharp-edge rectangular sluice gate in rectangular channel، and also suggest a discharge coefficient for combinational flow in different flow conditions. The experiments were carried out in laboratory channel on models with different geometric dimensions under various hydraulic conditions. Discharge coefficient was presented for various condition of passing flow of trapezoidal sharp-edge weir and below rectangular sluice gate using statistical analysis conducted on dimensionless geometric parameters affecting the flow. Resulting discharge coefficients were in agreement with laboratory results.

Side weir is used as a regulator structure to control discharge and water level in rivers and channels. A labyrinth side weir is a kind of weirs which does not have a direct and smooth edge in the plan view. When the opening length is limited, these side weirs can divert more water out of the channel by increasing the effective length. To evaluate performance of the side weir and estimate the rate of flow passing through it, the discharge coefficient should be determined. In this research, hydraulic behavior of a labyrinth side weir with a trapezoidal plan in the single-cycle has been studied experimentally. Upstream Froude number of the side weir was modified in each test andthe effects of opening length, height and side angels on the discharge coefficient were investigated. The results of the tests were analyzed to find out the effect of defined dimensionless parameters such as length, height and angle on the discharge coefficient in subcritical flow. The results obtained showed that in comparison with the normal side weirs the discharge coefficient of the trapezoidal labyrinth side weir increased about 15-30 percent. Also, the discharge coefficient decreased with increasing the Froude number and side angles and increased with increasing the opening length and height of the weir. In the range of experiments, the angle of 30 degrees gives the highest discharge coefficient that is approximately 1.5 times the other angles.